Question: 8 erasers cost $9.20. Which equation would help determine the cost of 6 erasers?
Explanation: There are several equations that could help determine the cost, each with a slightly different approach. Let $x$ represent the unknown cost of 6 erasers. Since 6 erasers cost $x$ , we have the following proportion: $\dfrac{6}{x}$ We can write the fact that 8 erasers cost $9.20 as a proportion: $\dfrac{8}{\$9.20}$ The cost changes along with the number of erasers purchased, and so the two proportions are equivalent. $\dfrac{6}{x} = \dfrac{8}{\$9.20}$